My Journey into Racing
#31
Rennlist Member
Awesome! What are you building?
I definitely felt like a dork after that was pointed out but at least it was an easy fix.
Bringing this up did make me think of a silly theoretical question for you though. Would there ever be an advantage to installing a wing upside down and using it to create lift? Not that I would ever do it but in my case where 65% of my weight is in the rear, is there a specific type of corner where lift would be an advantage?
I definitely felt like a dork after that was pointed out but at least it was an easy fix.
Bringing this up did make me think of a silly theoretical question for you though. Would there ever be an advantage to installing a wing upside down and using it to create lift? Not that I would ever do it but in my case where 65% of my weight is in the rear, is there a specific type of corner where lift would be an advantage?
so, yes, you could turn the wing upside down in the rear (or right side up as ACE mentioned ) and get lift in the rear.. cant think of too many situations where this would be something you would want to do.. maybe drifting at 130mph around willow springs comes to mind.
#32
Rennlist Member
Hahaha! Good poke, ace37. Slakker, in the data world, you are looking for "downforce," and fighting against "lift," so no. There are other ways to "unstick" either end more effectively and in pursuit of a more balanced car than introducing a condition the wing (and the car body shape) is designed to combat.
taking wing out, is lessing downforce and that is a common practice. now, since most wings make downforce (a lot sometimes) with 0 angle of attack and there are some cars that have a lot more lift up front, reducing rear downforce is something that sometimes needs to be reluctantly done in the pursuit of balance. sure, its a hypothetical qustion by Slacker, but the real answer is that sometimes yes, lift is reduced in the rear of the car. adding lift, is not common , but im sure there are situations where that is possible
Oh actually this might be interesting to you... while lift is undesirable in road racing, wings that offer high downforce often bring a penalty in added drag. One of the common causes of high drag is the use of aggressive wing angles of attack. When you set the same wing about flat relative to the airflow you'll typically get a great deal less drag than when you set it at 20-30 degrees for lots of downforce. Also, the drag penalty matters most at high speeds.
So so what quite a few clever race teams have done to gain an advantage (typically cheating) is use carefully selected wing materials that let the wing flex a bit at speed. Flex meaning the wind bends the wing shape to be a bit flatter at high speed, and the team usually has a good idea about how much this happens and at what speeds. Ergo lower high speed drag and still high low speed downforce in the moderate and low speed corners. Usually this is very subtle and hard to catch so it goes on for a while before being banned under movable aerodynamic device rules.
So so what quite a few clever race teams have done to gain an advantage (typically cheating) is use carefully selected wing materials that let the wing flex a bit at speed. Flex meaning the wind bends the wing shape to be a bit flatter at high speed, and the team usually has a good idea about how much this happens and at what speeds. Ergo lower high speed drag and still high low speed downforce in the moderate and low speed corners. Usually this is very subtle and hard to catch so it goes on for a while before being banned under movable aerodynamic device rules.
interesting that there are some techniques of materials that flex enough under aero forces, that change the shape enough to provide downforce when needed and flaten out , with those forces to reduce drag. those forces to distort are not free, so i wonder the drag effects to have such effects on the wing structure. do you have values of drag vs lift at different speed ranges for such a wing?
interesting.
Last edited by mark kibort; 01-20-2017 at 07:13 PM.
#33
Rennlist Member
interesting that there are some techniques of materials that flex enough under aero forces, that change the shape enough to provide downforce when needed and flaten out , with those forces to reduce drag. those forces to distort are not free, so i wonder the drag effects to have such effects on the wing structure. do you have values of drag vs lift at different speed ranges for such a wing?
interesting.
interesting.
http://www.mulsannescorner.com/newsjan15.html
http://www.mulsannescorner.com/newsjuly14.html
http://www.mulsannescorner.com/RCELeMans2014.html
Racecar engineering also did a short bit on it in August 2014.
Sorry, I don't know of any with hard numerical data available. It's not too hard to analytically estimate 2D airfoil chord stiffness though - to go dirt simple and intuitive you could consider a thin flat plate airfoil at 20 degrees. High aero pressure would bend it (especially near the trailing edge) to bleed off the angle of attack. If it needs to bend more just use a thinner piece of sheet metal. It can work pretty efficiently.
#34
Rennlist Member
Thread Starter
Originally Posted by GPA951s
I am building an 88 944 Turbo-s.
And as for uplift, yes, that was exactly the kind of theoretical informative but practically useless discussion I was hoping for. Thanks for taking the time to chime in guys.
#35
Three Wheelin'
[QUOTE=Slakker;13901147]Can't wait to see how it turns out! I'm not sure that a turbo can qualify but you should at least check into the 944cup series. The guy that runs it has been awesome to deal with on a few transactions and it sounds like a total hoot!
Plan is start out in PCA Stock F Get some seat time, Then move to the SP3 class..
Plan is start out in PCA Stock F Get some seat time, Then move to the SP3 class..
#36
Burning Brakes
-mike
#37
Rennlist Member
Why not just come straight to SP3? In F, you'll be classed with other letter cars, and will be the slower car in class. In SP3, you'll be with SP1-3 , usually SBOX, and occasionally D or E cars, usually a split start ( on east coast. anyway) so you'll be at the front end speed wise. I bought my car as an E car, and switched to SP3 after the first year. Should have started there, as it was just more competitive for my 968. Those E class 911s were tough to keep up with.
#38
Three Wheelin'
I have a Friend in the Club who races in "F" (Have to because of it being a turbo-s). I wanna go door to door with him here (Watkins is home track)... Then make the move to SP3..I think Ill backdate my car and put the smaller turbo on for SP3, 200 Extra pounds is not worth 30hp to me.. As it stands right now the only class I could run in Right away would be GT3 With the Setup I have on the engine stand...So I will Get my Racing License This summer and Do DE's with a REALLY fun car. I Really cant wait though! It looks like an absolute blast...